In recent years, the use of electronic control systems in plumbing fixtures has become increasingly popular. A deterrent to even more widespread use is believed to be mainly due to the greater cost compared to the basic mechanical type fixtures presently available. Although electronic control systems can provide desirable features, the cost and complexity of their installation tends to be a major drawback that prevents their full acceptance and use. Installation of standard manually operated plumbing fixtures requires only the services of a plumber, whereas installation of the electronic control system must include the labor cost for the electrical line power wiring needed to operate the mix actuator and the electronic controls. Another factor contributing to the installation cost of an electronic control system is the many separate components that must be installed.
Mixing valves presently used to control the mix temperature of hot and cold supply fluids have many different configurations and are installed frequently in plumbing fixtures such as showers and hand wash faucets. Mixing valves generally consist of two elements, the mix means for mixing the fluids and an actuator so that the mix means may vary the proportions of a hot and cold fluid to obtain a desired mix temperature. Both of the foregoing means are found in a great variety of forms, e.g., electric motors or solenoids in combination with poppet valves, gate valves, etc.
Presently, the electrical motor type actuator for mix proportioning and temperature control seems to be the most widely used. Although the electrical motor actuator has various desirable characteristics, such as adequate actuation forces and the capability of precision control, it inherently has various deficiencies for use as a mixing valve actuator. These deficiencies mainly are: relatively high electrical power consumption, especially when the electrical motor must move the mix means from extreme positions of hot to cold, cold to hot, and for other running adjustments which may require significant operation time. In some control systems, to provide a varying mix response, the electric motor actuator may require relays or other speed controls that could add extra complexity. Another objection to the electric motor actuator is that it needs a fluid-to-outside-air seal to separate it from the fluid of the mix mechanism. Since this is a moving or dynamic seal, it is subject to wear and eventual leakage. As this type of seal also needs sufficient compression forces to prevent fluid leakage, obtaining sufficient torques and low power consumption can also present problems. The fluid to air seal, in addition, is often subject to small seepages past the seal where dissolved minerals from the fluid precipitate out and can cause motor shaft binding. Mounting of the motor is another difficulty. If the motor shaft is not properly aligned with the seal, eccentric motion of the shaft with respect to the seal can occur causing either excess motor torque requirements, shaft binding, and uneven loads on the seal to cause premature fluid leakage. Since small electric motors for these applications have very high rotational speeds, they must be fitted with geared speed reduction units to provide adequate operating torque and a suitable speed reduction to operate the mix mechanism. Due to the high gear ratio, some means must be used to prevent the speed reduction output shaft from reaching an over torque condition that could result in speed reduction gear breakage. To overcome this problem, the electric motor needs a slip clutch, overtravel mechanism, or other means to protect the geared speed reduction from damage. All of these factors add to the complexity of the motor actuator or to the valve mix mechanism. As an example, where the motor operates a poppet type mix mechanism and the poppet is driven to its seated position, an abrupt increase of force occurs that could overstress the speed reduction gears unless some means is used to absorb or to divert the sudden force increase to the gears. Accordingly, one object of the present invention is to eliminate the need for the above mentioned seals and electric motor complexities. In achieving these objects a hydraulic actuator is employed and one such prior art actuator is shown in U.S. Pat. No. 3,561,481 to John F. Toplan which issued on Feb. 9, 1971.
Another object of this invention is to provide a single integrated packaged valve suitable for use in varied electronic control systems. The single integrated package will provide electronic control system designers and manufacturers the basic water mixing hardware for their control systems.
Still another object of this invention is to provide a mixing valve which will be operable with very low electrical power requirements. These low electrical operating requirements are the capability of a mixing valve to operate for long periods on readily available batteries. This capability has the advantage of eliminating the cost of an electrician for a power supply installation as is needed for a line powered mixing valve. In addition, the battery powered valve has the advantage of being operable even when a general electrical power outage occurs.